(a) Field of the Invention
The present invention relates to a display device including a touch panel device, and a method for eliminating a coupling noise between the display device and the touch panel device.
(b) Description of the Related Art
A display device of a liquid crystal display (“LCD”) and an organic light emitting device (“OLED”), a portable transmitting device, and other types of information processing devices execute a function thereof using various input devices, e.g., keyboards, mice, etc. Recently, the use of touch panels as an input device has increased.
The typical touch panel is a device for allowing a machine such as a computer to perform a desired command by writing a character, drawing a picture, or executing an icon through touching a finger or a touch pen (such as a stylus) on a screen. A display device to which the touch panel is attached can determine whether the finger of a user or a touch pen, etc., touches a screen, and touch position information thereof (the touch determination, i.e., the determination of whether a touch event occurred, and the positional information regarding the touch event may collectively be referred to as a “touch input”). The display device may then display images according to the position of the touch input.
These touch panels are typically classified as a resistive type, a capacitive type and an electro-magnetic (“EM”) type according to the method by which the touch is sensed.
Among the various types of touch panels, the resistive type of touch panel typically includes upper and lower transparent electrodes separated from each other by a spacer. If an upper plate formed with the upper transparent electrode is depressed by external contact such that the upper transparent electrode and the lower transparent electrode physically contact each other, the contact and the position of the contact may be determined by measuring a voltage change according to the resistance of the depressed position. The resistive type of touch panel may be operated regardless of the conductivity of the contact matter, however when several positions are simultaneously touched, the values of the changed voltages are recognized jointly as one contact such that it is difficult to obtain simultaneous touch information from the several positions.
The capacitance type of touch panel typically includes a film formed with a transparent electrode, and touch determination and touch positions may be determined by measuring a voltage change of the conductive matter by the user contact after applying a voltage to the transparent electrode. The user contact in this type of touch panel is typically supplied by the finger of the user. This capacitance type touch panel may determine the contact existence and the contact position even if various positions are simultaneously contacted, however the voltage change is not generated when an insulator, such as gloves or other non-conductive surface, contact the touch panel such that the contact information may not be obtained.
The touch panel may be further classified into an external type in which the touch panel is attached to an outside of the display device and an embedded type in which the touch panel is located inside the display device itself.
A display panel of the display device may include a plurality of switching elements for switching a data voltage, and a plurality of signal lines, such as gate lines and data lines, for applying the data voltage to a plurality of pixels by controlling the switching elements. The gate lines transmit a gate signal including a gate-on voltage Von and a gate-off voltage Voff. Signals applied to the display panel, and especially signals having relatively large widths such as the gate signal, influence a sensing output signal of both the embedded and external touch panel, thereby generating unwanted coupling noise which deteriorates the quality of the associated display.